Weights & ballasting


Hello Forum,

My 8th grade science class is building SeaPerch ROVs but they are incredibly positively buoyant with two floats attached to the top side of the PVC frame. I'm looking for ideas of weights to add that will help make these ROVs neutral in the water column. Removing some of the floats is an option but that affects the weight distribution of the ROV causing it to tilt.

Last year we used rocks but they were very difficult to attach to the ROV itself.

Something incremental and water-friendly that we could add about .5-1.5 lbs to one SeaPerch would be ideal.

Thanks for your thoughts!




Good luck with your project.

If you are using PVC Frame you could add on a closed section with a screw top so that you could pour in some lead shot

You can also use fishing line sinkers that come in different sizes, these have a loop on one end that you can tie them onto the frame.

I use copper pipe of various sizes and fill it with lead but in your case you don't need much weight so the fishing line sinkers may work best.


Hi Sarah:

Try using river sinkers. They have a loop on them that allows them to be zip-tied wherever they are needed.

Here's an example.

You can find these at any fishing store, or order them online.



We using fishing weights as the other posters suggested for our SeaPerches and zip tie them to the cargo net. We do a quick buoyancy test in a large bucket and let the students work out neutral buoyancy. It usually takes about three or four 4 ounce weights depending on how much pool noodle they have on their unit.


That was awesome!! I love to see how young people get so excited when they are involved in such a wonderful learning experience, and how the teachers and staff came together to make that happen. I would love to see that opportunity be available to every community, it is something that they will always remember and hopefully make career path decisions on and at some point in their life maybe they to can give back what they have learned.

Well Done and thanks for sharing.


Dave in Canada